Liquid carryover in production separator

[10815L]

Hi,
We are facing a problem with liquid carryover with gas. The separator is equipped with van type demister pad but gas outlet nozzle have demister. Gas outlet nozzle looks behaving like siphon. Separator is operating at 75psig and had flow rate is 4.5 MMSCFD. Gas valve is abot 25% open. Please any suggestion how to stop carryover problem.
Thanks
10815L

 

[TD2K]

A drawing of the unit would help with dimensions would help and gas/liquid properties.

Carryover is usually caused by too much gas flow. Have you check the vessel sizing against standard methods?

 

[zdas04]

It is also caused by velocity too low in the demister. I see that problem way more often than I see bulk vessel velocity too high. The mechanism of separation is very different in the two sections and trying to apply a drag model like Souder Brown to the mist pad (which requires a collision model) is a frequent source of them not working right.

David Simpson, PE
MuleShoe Engineering

In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual. —Galileo Galilei, Italian Physicist

 

[SatputeAjay]

Hi,

I had prepared the attached spreadsheet for separator sizing. Perhaps this could be one of the ways to check the size of your separator for its adequacy.

Regards.

Ajay S. Satpute

 

[SatputeAjay]

Hi,

I had prepared the attached spreadsheet for separator sizing. Perhaps this could be one of the ways to check the size of your separator for its adequacy.

Regards.

Ajay S. Satpute

(PS. Reposted)

 

[10815L]

Hi all,
the known is issue is small piping and control valve but this separator is sized for 21 MMSCFD gas, for more details please find attached P&ID.
Thanks
10815L

 

[10815L]

Hi all,
sorry, additional information, Flare gas PCV is adequate while PCV for Plant side is inadequate. carry over noticed both cases but quantity of liquid carryover is very high when gas open to plant because of PCV wide opening.
Thanks
10815L

 

[TD2K]

The link doesn't open for me. 4.5 MMscfd and 21 MMscfd also doesn't help much. What is the gas's MW? What is the temperature? What is the pressure?

 

[10815L]

Hi TD2K,
Here is Design Parameters; 50000BOPD, 50000BWPD and 21MMSCFD gas, MW 27, DP 150 psig and DT 200 0F
Operating parameters; 15000BOPD,21500BWPD and 4.5 MMSCFD. operating pressure 70-75 psig and temp 130 0F.
To me problem in demister pad orientation because this separator have vertical demister pad and gas outlet nozzle is without demister pad.
Thanks
10815L

 

[TD2K]

Do you have a drawing of the vessel? The P&ID would also help (the last link you posted didn't open for me).

 

[LittleInch]

What sort of liquid carryover are you getting?- Is it in the form of continuous spray / mist or is it coming over as discrete amounts?

Sectional drawing of the separator with liquid levels would help / essential to see what it is you're talking about.

What sort of incoming flow steady or slugging?

What is level control like - good or varies a lot

What was design intent of the vessel in terms of liquid in gas?

Has anything changed?

Give us some data and we might come up with more than general comments. We've got about 10% of what we need at the moment

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[10815L]

Hi,
significant amount of crude and water is coming in gas outlet stream, for first two minute continuous spray and then like mist.
incoming flow is smooth and continuous, i haven't seen any sign of slug flow.
levels are being controlled very good. The design intention to separate all three phase with maximum 0.1g/MMSCFD.
LittleInch, is it demister pad or PCV problem, as i noticed PCV is wide opening even gas flow is 3-4 MMSCFD.
Thanks
10815L